1. Field of the Invention
The present invention relates to connection units for mounting electronic components, such as ICs, or other micro-components to substrates. In particular, the present invention relates to a connection unit that is disposed between a component and a substrate and that has a simple, compact structure compared to conventional ones. The present invention further relates to a connection unit that allows an electronic component or other micro-components to be mounted on a substrate and allows the electronic component to be firmly fixed to the substrate after the electronic component is inspected for its electrical properties. Furthermore, the present invention relates to a method for fabricating such a connection unit.
2. Description of the Related Art
Japanese Unexamined Patent Application Publication No. 11-46059 discloses a structure for mounting an IC to a substrate. Generally, as disclosed in the above document, soldering balls provided on the bottom surface of the IC are heat-melted to fix the solder to wiring patterns provided on a substrate, whereby the IC can be electrically connected to the substrate. Alternatively, an IC socket is used to mount the IC to the substrate.
However, for a small-sized IC, the use of soldering balls, as in the above document, may lead to, for example, a short circuit between the soldering balls disposed below the IC. Furthermore, the soldering balls must be uniform in size so that the IC can be properly fixed to the substrate. However, since the soldering balls must be reduced in size in proportion to the size reduction of the IC, it is becoming more difficult to form soldering balls that are uniform in size.
With such a structure for mounting an IC to a substrate using soldering balls, the inspection for the electrical properties of the IC is generally performed after the soldering balls are heat-melted for fixing the balls to the substrate.
If the IC is determined defective in the inspection process, it is extremely difficult to remove the IC since the IC is already fixed to the substrate. This is time-consuming and thus may lower the productivity rate.
On the other hand, in a case where an IC socket is used, the IC is disposed in the IC socket and can readily be dismounted from the IC socket. For this reason, even if it is determined that the IC is defective in the inspection process, the replacement of the IC is relatively easier compared to the case where the soldering balls are used.
However, as shown in FIG. 7 of the above document, for example, an IC socket is an extremely large component that occupies a large portion of the substrate, and therefore, does not comply with the demand for size reduction.
Furthermore, if there is a significant difference in thermal expansion coefficients between the substrate and the IC, a heat treatment during the fabrication process, for example, can cause a large distortion between the substrate and the IC. This may be problematic in that the IC cannot be properly and firmly mounted on the substrate.